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[英]How to avoid observable delay in angular or make sure my function gets called only when observable is ready
[英]Understand how the anonymous function in ready gets called
我在这里只是通过这段代码,它描述了如何在纯js中创建自己的自定义ready函数。 答案被详细解释,我已经在js中编程了一段时间了,但是在理解代码的初始部分时仍然有一个问题,请再次看下面的代码:
(function(funcName, baseObj) {
// The public function name defaults to window.docReady
// but you can pass in your own object and own function name and those will be used
// if you want to put them in a different namespace
funcName = funcName || "docReady";
baseObj = baseObj || window;
var readyList = [];
var readyFired = false;
var readyEventHandlersInstalled = false;
// call this when the document is ready
// this function protects itself against being called more than once
function ready() {
if (!readyFired) {
// this must be set to true before we start calling callbacks
readyFired = true;
for (var i = 0; i < readyList.length; i++) {
// if a callback here happens to add new ready handlers,
// the docReady() function will see that it already fired
// and will schedule the callback to run right after
// this event loop finishes so all handlers will still execute
// in order and no new ones will be added to the readyList
// while we are processing the list
readyList[i].fn.call(window, readyList[i].ctx);
}
// allow any closures held by these functions to free
readyList = [];
}
}
function readyStateChange() {
if ( document.readyState === "complete" ) {
ready();
}
}
// This is the one public interface
// docReady(fn, context);
// the context argument is optional - if present, it will be passed
// as an argument to the callback
baseObj[funcName] = function(callback, context) {
// if ready has already fired, then just schedule the callback
// to fire asynchronously, but right away
if (readyFired) {
setTimeout(function() {callback(context);}, 1);
return;
} else {
// add the function and context to the list
readyList.push({fn: callback, ctx: context});
}
// if document already ready to go, schedule the ready function to run
if (document.readyState === "complete") {
setTimeout(ready, 1);
} else if (!readyEventHandlersInstalled) {
// otherwise if we don't have event handlers installed, install them
if (document.addEventListener) {
// first choice is DOMContentLoaded event
document.addEventListener("DOMContentLoaded", ready, false);
// backup is window load event
window.addEventListener("load", ready, false);
} else {
// must be IE
document.attachEvent("onreadystatechange", readyStateChange);
window.attachEvent("onload", ready);
}
readyEventHandlersInstalled = true;
}
};
})("docReady", window);
我这样调用代码:
docReady(function() {
alert('hello');
}, window);
我的问题是,如何像这样调用匿名函数? ..我完全困惑:(
甚至下面的代码如何工作?
docReady(function() {
alert('hello');
}, window);
我的意思是没有定义明确的docReady函数,如下所示:
docReady function (param1, param2);
我所看到的只是docReady作为参数传递给匿名函数吗?
baseObj[funcName] = function(callback, context) {
相当于
window["docReady"] = function(callback, context) {
它将函数声明为window
的属性(全局对象),这意味着您可以使用
window["docReady"](function() {
alert('hello');
}, window);
或搭配
window.docReady(function() {
alert('hello');
}, window);
甚至
docReady(function() {
alert('hello');
}, window);
因为全局对象的属性也是全局作用域(以及阴影之前的任何内部作用域)的变量。
关键位是baseObj[funcName] = function
此时, baseObj
是(或至少可以是) window
, funcName
是(或可以是) docReady
。
因此,此时它向window
(全局)添加了一个名为“ docReady”的函数
window
和“ docReady”作为默认参数传递到最后一行
})("docReady", window);
其中在顶部将函数作为参数输入(function(funcName, baseObj) {
NB当我说baseObj
是(或至少可以) window
,那是因为你可以重写此值,则该行:
funcName = funcName || "docReady";
baseObj = baseObj || window;
如果未提供替代方法, baseObj
funcName
设置为“ docReady”和baseObj
,这意味着您可以根据需要更改它们,因此如果最后一行更改为})("getReady", myObject);
该函数将称为getReady并将其添加到myObject
而不是全局window
您正在阅读错误的代码。
检查以下行:
(function(funcName, baseObj) {
...
baseObj[funcName] = function(callback, context) {
...
};
...
})("docReady", window);
它将为baseObj
添加一个新属性,在本例中为window
。 该属性是您调用的函数。 docReady
。 全局的所有东西都不需要像window.something
这样的名字。 这就是为什么您使用docReady
的原因。
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